Another top reason for avoiding formats other than Word or a plain text file is that it becomes increasingly more difficult to download into many HR and recruiting systems. Often a recruiter will not have a job for you today. If they cannot enter your resume into their recruiting system, they will be unable to match your resume with any positions that do become available. This also goes for mailed and faxed resumes. Unless specifically requested otherwise, recruiters are looking for easy to open Word Attachments.
http://www.jobseekersadvice.com/cv-and-resume/recruiters-spend-less-than-10-seconds-reviewing-a-cv/
However, it has been my experience that most recruiters prefer Word documents because of the ability to tweak the resume for particular job orders, opportunities or to add additional bullets, experience, and skills that may be applicable for the specific position to which they are applying. I, myself, lean this way because I believe that resumes should be tailored to each job posting in order to increase the likelihood of interviews and job offers. That, in the end, is the goal of any job search.
http://www.linkedin.com/answers/hiring-human-resources/staffing-recruiting/HRH_SFF/929180-2246826